1. Field of the Invention
This invention relates to electronic musical tone synthesis and in particular is concerned with the generation of tones that have a percussive transient at the start of the tone.
2. Description of the Prior Art
A feature commonly used with electronic keyboard instruments intended for producing popular music is one that is given the generic name of "percussive voice". This is usually a composite voice including a first tone having a piano-like ADSR (attack/decay/sustain/release) envelope played in combination with an organ-like sustained tone. The musical effect is a transient percussive sound at the onset of tonal production.
In U.S. Pat. No. 3,740,450 entitled "Apparatus And Method For Simulating Chiff" a system is described for producing chiff tones in a digital organ of the type wherein a musical waveshape is repetitively read out of storage at a rate related to the selected note. A chiffing waveshape is stored in a separate memory that is accessed during the attack portion of the primary tone. The separate waveshape memory outputs are combined to produce the chiffed musical tone.
In U.S. Pat. No. 3,913,422 entitled "Voicing For A Computer Organ" a system is described for producing chiff tones (otherwise called transient or percussive tones) in an organ of the type described in U.S. Pat. No. 3,809,786. In this system, musical tones are produced by computing in real time the amplitudes x(gR) at successive sample points gR of a musical waveshape and converting these amplitudes to musical tones as the computations are carried out. The tonal quality of the generated note is established by a set of harmonic coefficients. Transient voices are obtained by adding selected harmonics to the set of harmonic coefficients for a short interval at the onset of the generated waveshape.
In U.S. Pat. No. 4,122,742 entitled "Transient Voice Generator" a polyphonic system is described for producing musical tones having a time variant change by computing master and transient data sets, transferring these data to buffer memories, adding the data read out from the buffer memories briefly during a transient time interval and repetitively converting the summed data to waveforms. The master and transient data set are created repetitively and independently of tone generation by computing a generalized Fourier algorithm using stored sets of Generalized Fourier coefficients.